The North Dakota State Highway Department found cracking in concrete on Interstate Highway 94 east of Dickinson in about 1979 when the concrete was about 15 years old. While the cracking was primarily in the eastbound lanes where high-alkali portland cement had been used, it had the appearance of 'D' cracking. The fine aggregate was local natural sand with a good service record, while the coarse aggregate was a mixed gravel from eastern Montana with no known service record. The question therefore was: Is the cracking due to alkali-silica reaction to freezing and thawing, or to both, or to some other factor or factors? Petrographic examination of concrete cores from the cracked pavement and dilation testing of some of these for resistance to freezing and thawing showed the presence of significant amounts of products of alkali-silica reaction and satisfactory frost resistance. It was concluded that the cracking was due to alkali-silica reaction.

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